BACKGROUND: The aims of this study were to analyze the association of oral breathing with dental malocclusions and aspects of general health such as acute illnesses, oxygen saturation in blood and its possible implication in the process of nutrition.METHODS: A prevalence analytic study was carried out. Five dentists explored to children between 6 and 12 years and measured their oxygen saturation. Parents completed a questionnaire of 11 items about general health (colds, ear infections, tonsillitis and taking antibiotics) and the food preferences of their children. At the end, children were classified in oral breathing group (prevalence cases) or nasal breathing group (controls).RESULTS: There were statistical differences between cases (452 children) and controls (752 children) in the facial morphometric measurements. Oral breathing children had statistically less percentage of oxygen saturation than controls (92.3±3.3% versus 96.5±2.3%), took less time to have lunch and preferred less consistent and sugary food. Cases had had more prevalence of pathologies in the last year and of taking the antibiotics. This group also had higher prevalence of allergies compared with controls group (P<0.001).CONCLUSIONS: Oral breathing is significantly associated with specific dental malocclusions and important aspects of general health such as oxygen saturation and the nutrition. On the same line, oral breathing is related to a significantly higher prevalence of allergies and a significantly more likely getting sick and taking medication.